I-5 Ship Canal SW Facility
Hydrologic Flow Analysis
October - December 2025
Overview
This analysis compares monitored (Manning equation) and modeled stormwater discharge flows at the I-5 Ship Canal SW Facility for both WSDOT and City of Seattle drainage systems. Rainfall data from rain gauge RG33 is included for context.
Key Findings
WSDOT (I-5)
| Metric | Monitored | MGSFlood Modeled | Difference |
|---|---|---|---|
| Total Volume | 40,655,414 gal | 46,784,784 gal | -6,129,369 gal (-13.1%) |
| Peak Flow Rate | 18.49 cfs | 22.2 cfs | -3.71 cfs (-16.7%) |
City of Seattle - U District (MGSFlood Modeled)
| Metric | Monitored | MGSFlood Modeled | Difference |
|---|---|---|---|
| Total Volume | 23,276,461 gal | 42,491,168 gal | -19,214,706 gal (-45.2%) |
| Peak Flow Rate | 7.15 cfs | 20.5 cfs | -13.35 cfs (-65.1%) |
City of Seattle - U District (MGSFlood Conveyance)
| Metric | Monitored | MGSFlood Conveyance | Difference |
|---|---|---|---|
| Total Volume | 23,276,461 gal | 42,470,781 gal | -19,194,320 gal (-45.2%) |
| Peak Flow Rate | 7.15 cfs | 19.6 cfs | -12.45 cfs (-63.5%) |
WSDOT (I-5): Monitored vs Modeled Flow
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City of Seattle - U District: Monitored vs Modeled Flow
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WSDOT (I-5) vs City of Seattle - U District Comparison
Monitored Flows
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Modeled Flows
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All Flows Overview
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Generated: 2026-02-03 14:48:31.463858
Data Source: AQUARIUS
| Analysis Period: October 1 - December 31, 2025